﻿/********************************************************
 *  ██████╗  ██████╗████████╗██╗
 * ██╔════╝ ██╔════╝╚══██╔══╝██║
 * ██║  ███╗██║        ██║   ██║
 * ██║   ██║██║        ██║   ██║
 * ╚██████╔╝╚██████╗   ██║   ███████╗
 *  ╚═════╝  ╚═════╝   ╚═╝   ╚══════╝
 * Geophysical Computational Tools & Library (GCTL)
 *
 * Copyright (c) 2023  Yi Zhang (yizhang-geo@zju.edu.cn)
 *
 * GCTL is distributed under a dual licensing scheme. You can redistribute 
 * it and/or modify it under the terms of the GNU Lesser General Public 
 * License as published by the Free Software Foundation, either version 2 
 * of the License, or (at your option) any later version. You should have 
 * received a copy of the GNU Lesser General Public License along with this 
 * program. If not, see <http://www.gnu.org/licenses/>.
 * 
 * If the terms and conditions of the LGPL v.2. would prevent you from using 
 * the GCTL, please consider the option to obtain a commercial license for a 
 * fee. These licenses are offered by the GCTL's original author. As a rule, 
 * licenses are provided "as-is", unlimited in time for a one time fee. Please 
 * send corresponding requests to: yizhang-geo@zju.edu.cn. Please do not forget 
 * to include some description of your company and the realm of its activities. 
 * Also add information on how to contact you by electronic and paper mail.
 ******************************************************/

#ifndef _GCTL_FFT_H
#define _GCTL_FFT_H

// library head file
#include "../gctl_config.h"
#include "../core.h"

// fftw head file
#include "fftw3.h"

namespace gctl
{
    /**
     * @brief      1D Discrete Fourier Transform (DFT) from real data to complex spectrum.
     *
     * @param[in]  in_real   Input real data array of size n
     * @param      out_spectrum  Output complex spectrum of size n/2+1
     * @param      sampling Sampling freqency, this is needed to calculate the output frequency index
     * @param      freq_ptr Output frequency index of size n/2+1
     */
    void dft_r2c_1d(const _1d_array &in_real, _1cd_array &out_spectrum, double sampling = 0, _1d_array *freq_ptr = nullptr);

    /**
     * @brief 1D Discrete Fourier Transform (DFT) from complex spectrum to real data.
     * 
     * @param in_spectrum Intput complex spectrum of size n
     * @param out_real Output real data array of size 2*(n-1) 
     */
    void dft_c2r_1d(const _1cd_array &in_spectrum, _1d_array &out_real);

     /**
     * @brief      2D Discrete Fourier Transform
     *
     * @param[in]  in_arr   Input real array
     * @param      out_arr  Output complex array
     */
    void dft2d(const _2d_matrix &in_arr, _1cd_array &out_arr);

    /**
     * @brief      2D Inverse Discrete Fourier Transform
     *
     * @param[in]  in_arr   Input complex array
     * @param[in]  m        Row size of the 2D matrix
     * @param[in]  n        Column size of the 2D matrix
     * @param      out_arr  Output real array
     */
    void idft2d(const _1cd_array &in_arr, int m, int n, _2d_matrix &out_arr);

    /**
     * @brief      1D Discrete Cosine Transform
     *
     * @param[in]  in_arr   Input real array
     * @param      out_arr  Output real array
     */
    void dct1d(const _1d_array &in_arr, _1d_array &out_arr);

    /**
     * @brief      1D Inverse Cosine Fourier Transform
     *
     * @param[in]  in_arr   Input real array
     * @param      out_arr  Output real array
     */
    void idct1d(const _1d_array &in_arr, _1d_array &out_arr);
}

#endif // _GCTL_FFT_H